Flame inhibiting and retarding chemical compositions for general use on multiple solid surfaces

ABSTRACT

A product to render flame- and fireproof surfaces and materials and inhibit the spread of fire on objects of various and diverse chemical nature and affinity, using non-toxic and non-carcinogenic basic fire and flame retardant intumescent mixtures with wide ranging chemical affinity, prepared in stable colloidal dispersion. The intumescent base comprises a colloidal solvent in which a source of phosphoric acid, a charring agent and a blowing agent are dissolved and dispersed. Intumescent mixtures are produced adding to said base flame spread reduction materials, thermal resistance enhancers, thermal transmission reduction and refractory, elasticity, water resistant materials and combinations thereof. Bipolar chemicals are also added to change the chemical affinity. Products are applicable on household, professional and industrial materials and objects, natural, synthetic and metallic.

This application is a divisional of Ser. No. 09/492,482, filed Jan. 27,2000 now U.S. Pat. No. 6,613,391.

The present invention relates to a process for flame- and fireproofingsurfaces, substrates, and materials of various and diverse composition,comprising natural, synthetic and metallic materials. The inventionrelates more particularly to the readily achievable application of anintumescent fire- and flame retarding composition to coat smooth,non-porous, as well as porous surfaces. The invention further disclosesa novel fire- and flame retarding composition based on dissolvingsoluble materials dispersing and suspending insoluble materialscolloidally in a water-based formulation, and further describesprocedures for modifying the polarity of said flame retardingcomposition, where needed, to achieve the desired coating effect onsynthetic and metallic surfaces. Furthermore, the composition hereindisclosed comprises non-toxic materials.

BACKGROUND OF THE INVENTION Prior Art

In the prior art it is almost always specified what kind of material theretardant is to be applied to, with substantial differences incomposition depending on the actual substrate to be protected.

Furthermore, in most cases the materials to be applied are unsafe, toxicor noxious, making them unsuitable for household use or for otherpurposes which entail human contact or handling; furthermore, theirpreparation and/or application may entail cumbersome and involvedtechniques. Presently published fire retardant literature does notdisclose the need to keep the fire retardant mixtures in suspension ascolloidal mixture to obtain the desired fire protecting quality of amixture, and to increase and enhance the shelf-life of the product.

Currently there is no single intumescent-based fire-retardant coatingmaterial having all of the following features:

1. a coating material allowing ease of application by spraying,brushing, roller application, or the like; and,

2. a coating material maintaining its consistency over time and keepingall of its components perfectly mixed and blended with one another in acolloid state; and,

3. a coating material that can be applied with minor variations to alarge variety and diversity of substrates;

4. a coating material comprising non-toxic or minimally toxicingredients;

5. a coating material that is suspended in a water based solvent to benon-toxic or having no toxicity when applied, after curing on all kindsof surfaces, including wood, plastics, sheetrock, toys, formica, rubber,etc.; and,

6. a coating material providing a low rate of thermal transmission,especially where low weight is critical, such as in aircraft and ships;

7. a coating material drying quickly and efficiently;

8. a coating material with good adhesion and stability.

9. a coating material for home and non-professional use.

10. a coating material for incorporation and application in buildingmaterials and structures.

None of the so-far disclosed flame retardant compositions teach theprocess and principles outlined in the present application. U.S. Pat.No. 4,198,328, issued to Bertelli, discloses flame-resisting paintsobtained by reacting aldehydes with compounds containing amido, carbonyl(>C═O), and >C═S containing compounds inserted in a cyclic structure, orreaction products from aliphatic or aromatic diisocyanates ortriisocyanates with organic compounds having reactive hydrogen atoms.U.S. Pat. No. 4,224,374, issued to Priest, discloses a non-flammableimpregnant for polyether-derived polyurethane foam substrates,characterized by a carboxylated neoprene latex and alumina trihydrate.U.S. Pat. No. 4,370,442, issued to Pearson, discloses an aqueousresinous system produced by reacting an aldehyde with phosphoric acid,and adding an alkanolamine, urea, and melamine in aqueous solution. U.S.Pat. Nos. 4,380,593 and 4,740,527 issued to Von Bonin, discloseintumescent products obtained by a complex reaction sequence employingpolyisocyanates as starting materials. U.S. Pat. No. 4,603,226, issuedto Vajs et al., discloses a flexible coating providing protection up to1000° C., obtained in two stages; a first stage produces an intumescentfoam layer and the second relies on vitrification of an agent carried inthe intumescent layer, preferably a silicic base. U.S. Pat. Nos.4,879,320 and 4,963,296, issued to Hastings, disclose a fluidintumescent film-forming binder such as polyvinyl acetate, acrylicresin, vinyl acrylic resin, silicone resin, epoxy or polyurethane, orcombinations thereof, that can be rendered electrically conductive byincorporating conductive particles. U.S. Pat. No. 5,401,793, issued toKobayashi, discloses the use of carbides, borides, nitrides, syntheticresins containing phosphorus and/or sulphur, and other compounds capableof forming Lewis bases on heating. U.S. Pat. No. 5,723,515, issued toGottfried, discloses a fluid intumescent base material, whichadditionally includes a binding agent, solvents, and pigment, with theaddition of flame spread, oxygen and thermal transmission reducingmaterials, refractory fibers, mechanical enhancers, water resistant andelasticity agents.

Furthermore, none of the currently disclosed flame retardant compositionteaches the use of colloid forming compositions to obtain a stable,paste-like, easy to apply flame suppressant and fire retardant product.

OBJECTS, FEATURES, AND ADVANTAGES OF THE INVENTION

1) In accordance with the above stated needs and the prior art is theobject of the present invention to disclose unique fire retardantprocedures, to apply fire retardant mixtures to a whole variety of solidsurfaces, equally effective on wood, paper, styrofoam, polystyrene,rubber tubing, vinyl tubing, PVC tubing, iron, steel, stainless steel,aluminum and other non-ferrous metals, etc.2) Another object of the present invention is to disclose a flameretardant mixture consisting of an intumescent base comprised of watersoluble materials dissolved in a colloidal solution, and water insolublematerials dispersed or suspended in colloidal form in said colloidalsolution. The colloidal solution is formed dissolving macromolecularmaterials—such as carbohydrates and proteins—in water prior to theaddition of any further materials. The purpose of colloidallydissolving, dispersing, and suspending materials is to keep the fireretardant mixture evenly distributed, and permanently suspended, thusavoiding precipitation of the insoluble material during storage,application, and providing a uniform flame and fire retardant coating.

Intumescent fire retardant mixtures comprise a source of phosphoricacid, a charring agent, and a blowing agent. Upon exposure to fire,phosphoric acid is generated, which catalyzes the formation of a charlayer and the generation of non combustible gases which oppose thesupply of oxygen to the fire. The surface char layer both insulates fromfurther thermal degradation and impedes the flow of potentiallyflammable decomposition products from the interior of the product to thegas phase where combustion occurs. Intumescent mixtures furtherinterfere with the supply of oxygen to the flame by blowingnon-combustible gases generated by the fire and flame themselves, thuscausing the flame to eventually subside and die.

3) Another object of this invention is to disclose a paste-like,colloidally stabilized, flame retardant mixture, wherein fillers, andelasticity agents such as milled Fibers, paper, vermiculite, perlite,and the like, are added to give a paste like consistency to the mixture;said mixture also including fire and heat refractory fibers andmaterials, flame spread reagents, thermal transmission agents, andoxygen reducing agents, to provide protection at elevated temperatures,as high as 3500-4000° F.4) A feature of the present invention is a colloidal fire retardantmixture that can be mixed with a water based resin, that, upon curing atroom temperature, with or without addition of an accelerator, adheres tosynthetic substrates, previously impervious to the application of theoriginal flame retardant mixture.5) Another object of the present invention is to disclose a process toapply a replacement fireproofing cementitious compound For steelstructures, pipes, etc. fire retardant mixture on a variety of substratematerials, such as wood, plywood, formica, plastics, PVC, rubber,composites, vinyl, styrofoam, sheetrock, ceiling, tiles, etc.Cementitious fireproofing materials are substitutes for asbestos, whenasbestos is removed.6) A further feature of the present invention is to disclose a processto apply a fire retardant materials for use in many industries, such asconstruction, transportation, utilities, telecommunications, chemicaland petroleum manufacturing, aircraft, marine crafts, industrial,domestic and military applications.7) A further feature of the present invention is to disclose a processusing non-toxic products.

ADVANTAGES OF THE PRESENT INVENTION

Accordingly, one of the advantages of the present invention is that itprovides for a stable intumescent fire retardant coating compositionthat is effective on a variety of solid substrates that displaydifferent chemical interactions with the fire retardant.

Another advantage of the present invention is that the stability of theintumescent base is made possible by the formation of a thick colloidalmixture which keeps insoluble particles hydrated and suspended in thesolution. As a matter of fact, the full stabilization of the mixturerequires 3-5 days to take effect.

Another advantage of the present invention is that the applicability ofthe rather polar intumescent mixture for synthetic and non-polarsurfaces is obtained through the application of an alkaline water basedresin, which decreases the ionic character and polarity of the mixture.The resin itself, dispersed in the mixture, polymerizes slowly andgradually at room temperature creating a loose molecular network whichenvelopes the intumescent material. The more polar groups of the resinappear to be turned inwards while the less polar groups of the resin areturned outwards towards the unpolar substrate, thus binding to it byhydrophobic and Van der Waals bonds. Another advantage of the presentinvention is that it allows for the addition of colored pigments, sothat the paste can be used as paint for decorative purposes in homes,business and industrial settings.

Yet another advantage of the present invention is that is that a similarcombination can be used in glues, so that fire retardant glues can beproduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow diagram of the procedure.

FIG. 2 is a summary of the chemical-substrate interactions with theflame retardant.

DRAWINGS

FIG. 1

Flow diagram for the procedures to follow to obtain the flame retardantmixtures of this patent application and apply them to flame- andfireproof substrates and materials, comprising the following steps:

1. Colloidal solvent—dissolving colloid forming agent in water.

2. Intumescent base—adding blowing, charring, and foaming agents.

3. Intumescent mixture—comprising the steps of adding flame spreadreduction agents, thermal transmission reduction agents, refractoryfibers, temperature protection enhancers, elasticity agents.

These products can be used on paper, wood, cellulose, polystyrene,styrofoam, natural rubber, etc.

4. Resin-intumescent mixture—step a) add accelerator to water-basedresin; step b) add resin-accelerator mixture to intumescent mixture.

This product can be used clear metallic surfaces, synthetic materials,and other similar substrates.

FIG. 2

Substrate-Retardant Interactions:

A) Ionic, ion-dipol: Interaction between intumescent mixture and naturalsurfaces, including porous materials, such as styrofoam and polystyrene.

B) Primer-like surface on substrate under weak alkaline conditions.Weakening of ionization on flame retardant intumescent mixture by theaddition of a water-based resin, and formation of an envelope-likelattice, with hydrophilic interior and hydrophobic exterior, by gradualpolymerization of the resin. This process modifies the polarity of theintumescent mixture, making the adhesion and coating to the non-polarsubstrate possible.

SUMMARY OF THE INVENTION

The present invention provides an intumescent, colloidal, fire retardantmixture, comprising an intumescent base material, and other flame andfire retarding and quenching chemical means dissolved or finelydispersed and stabilized in a colloidal solution. This intumescentmixture is further miscible with a water-based resin, which enables thematerial to be spread and adhere onto a variety of synthetic andmetallic substrates, which otherwise would not be chemically compatiblewith the flame retardant base itself, and thus would reject the fireretardant material.

The combination of the intumescent composition with the first colloidforming solution and with the second water soluble resin produces anunexpected and unusual fire retardant coating. This coating hasreasonable affinity for all kinds of solid surfaces, natural, synthetic,and metallic, and allows for uniform application of and coating with afire retardant mixture on a variety of solid surfaces, both porous andnon-porous, natural, synthetic, and metallic. The coating material canbe applied onto most solid substrates, such as wood, cellulose, rubber,styrofoam, vinyl, PVC, sheetrock, formica, composite, etc. Thesematerials can thus be used for the fireproofing of cardboard containers,formica based furniture, styrofoam containers and packing materials,ceiling tiles, building walls, ceiling beams, wood poles, and the like.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present invention, the preferred embodiments and examples includethe following:

Embodiment 1 Example 1-1

Colloid dispersing solution (CDS): A colloid dispersing solution isprepared by dissolving 50 g hydroxyethylcellulose (HEC)(“CELLOSIZE”,Union Carbide) in 1000 g water (5%). The mixture is allowed to clearwith occasional stirring.

Intumescent base (IB): To the colloid dispersing solution are added insuccession 125 g urea, 125 g melamine, and or amino acid mixtures, 100 gglycerol, and 150 g starch. The volume of the mixture increases to 1500ml. To maintain the concentration of HEC in the mixture, 25 g of themodified cellulose is added to the mixture. If the volume at this pointis different, the addition of HEC would be 5% of the volume increase.After thorough mixing, 300 g ammoniumpolyphosphate is added to themixture.

Intumescent mixture (IM): Then, in the order, the following materialsare added under thorough mixing and homogenization: 75 g aluminumhydroxyde, 67.5 g aluminum trioxide, 56.25 g silicone dioxide, 75 gtitanium dioxide, 67.5 g zirconium dioxide, 27 g kaolin, and 50 g glasspowder.

The mixture is thoroughly mixed and left for 2-3 days before use.

This mixture is coated onto the substrates by brushing, roller,spraying, or any other suitable means.

Example 1-5

The intumescent base for the mixture is prepared by adding to thecolloid dispersing solution 125 g urea, 125 g melamine, 100 g glycerol,and 150 g starch. The volume of the mixture increases to 1500 ml, but nofurther. HEC is added to compensate for the dilution. All other steps ofExample 1-1 are followed as described.

Example 1-6

The intumescent mixture is prepared by adding to the intumescent base ofExample 1-1 300 g ammonium polyphosphate, 75 g aluminum hydroxide, 67.5g aluminum trioxide, 56.25 g silicone dioxide, 75 g titanium dioxide,and 67.5 g zirconium dioxide. All other steps of Example 1-1 are kept asdescribed.

Example 1-7

The intumescent mixture is prepared by adding to the intumescent base ofExample 1-1 150 g ammoniumpolyphosphate, 50 g aluminum hydroxide, 45 galuminum trioxide, 37.5 g silicone dioxide, 50 g titanium dioxide, 45 gzirconium dioxide, 27 g kaolin, and 50 g glass powder. All other stepsof Example 1-1 are kept as described.

Example 1-8

The colloid dispersing solution is prepared with 3% HEC (30 g per 1000 gwater). All other steps of Example 1-1 are kept as described.

Example 1-9

The colloid dispersing solution (CDS) and the intumescent base (IB) isprepared as described in Example 1-1. The mixture is let stand for a fewdays, until the sediment settles and the supernatant is clear. Thesupernatant is separated, and 5-20% w/v of a mixture of 9:1 diammoniumphosphate:monoammonium phosphate is added gradually with stirring. Thesolution is clear. This solution is then used as a flame-quenchingspraying fluid for a variety of applications.

Example 1-10

The colloid dispersing solution is prepared as described in Example 1-1.Then 20% urea, 10% glycerin, and 15% dextrin are added in sequence,waiting for each following addition step until the previous one has beendissolved. Finally, 10-20% of a mixture of 9:1 diammoniumphosphate:monoammonium phosphate is added, making sure that no break-upof the colloid takes place. This solution/dispersion is used as a liquidflame and fire quenching spraying fluid for a variety of applications.

Embodiment 2 Example 2-1

An aliquot of the mixture of Examples 1-1 through 1-8 is further treatedas follows:

Resin-Intumescent Mixture:

Resin-accelerator mixture (RAM): Aqueous melamine resin (a partiallyalkylated, partially polymerized hexamethoxymethylol melamine —“AEROTEX3430”) containing 0.5-2% formaldehyde (BF Goodrich Chemicals) is mixedwith 3% accelerator (diammonium phosphate or “FREECAT 187” from FreedomChemicals). After mixing the solution becomes slightly turbid.

Resin-intumescent mixture (RIM): One part RAM is added to 3-5 parts ofthe intumescent mixture of Example 1-1. It is thoroughly mixed and letstand for 1-2 hours. The mixture is then applied by brushing, roller,spraying, or any other suitable means onto vinyl surfaces, PVC, gardenhoses, steel supporting beam, steel structures, metal components,building components (door frames, doors, window and window frames, etc.)for full fire protection and adhesion to the substrates. Thepolymerization reaction of the melamine, catalyzed by the accelerator,proceeds slowly at room temperature and generates an even, smooth andflexible, adhesive coating on the substrate.

Example 2-2

Resinous Intumescent Mixture:

The resin-accelerator mixture (RAM) is prepared as in Example 2-1 and analiquot of the intumescent mixture as in Examples 1-1 through 1-8 isused. One part RAM is added to 2 parts of the intumescent mixture ofExample 1. The mixture is thoroughly mixed and let stand for 1-2 hours.It is applied by brushing, roller, or any other suitable means ontovinyl surfaces, PVC, garden hoses, metal surfaces, etc. for full fireprotection. The polymerization reaction of the melamine, catalyzed bythe accelerator, proceeds slowly at room temperature and generates aneven, smooth and flexible, adhesive coating on the substrate.

Example 2-3

An aliquot of the mixture of Example 1-1 through 1-8 is further treatedas follows:

Resin-Intumescent Mixture:

Resin accelerator mixture: Aqueous melamine resin (partially alkylatedtrimethoxymethylol melamine —“AEROTEX M3” containing 0.5-2.0%formaldehyde (BF Goodrich) is mixed with 3% accelerator (diammoniumphosphate or “FREECAT 187” from BF Goodrich). All other details andsteps of the preparation are described in Example 2-1.

Example 2-4

An aliquot of the mixture as in Example 1-1 through 1-8 is furthertreated as follows

Resin-Intumescent Mixture:

Resin-accelerator mixture: Aqueous melamine resin (“AEROTEX 3430” or“AEROTEX M3” from BF Goodrich) containing 0.5-2.0% formaldehyde is mixedwith 5% accelerator (as per other examples All other details and stepsof Example 2 are followed as described.

Example 2-5

Resin-intumescent mixture: 1 Aliquot aqueous melamine-based resin (asper above examples) is mixed vigorously with 2-5 aliquots intumescentmixture of examples 1-1 through 1-8. To this mixture 3-5% accelerator asper previous examples is added under vigorous mixing. The rest of theprocedure is as described in examples 2-1 through 2-4.

Embodiment 3 Example 3-1

A thin coat of a silicone-based primer, such as “SS 4179” (GE Chemicals)is applied onto the substrate by brushing, roller, or any otherappropriate method, and let dry, possibly overnight. This treatmentproduces an intermediate coat over the substrate, onto which thepreparation of Examples 1-1 through 1-8 is then applied as described inExample 1.

This treatment causes the intumescent mixture to adhere quite firmly tosynthetic and non-porous substrates such as vinyl, PVC, garden hoses,etc., that otherwise would reject any contact with the intumescentmixture.

Example 3-2

The treatment of Example 3-1 is enhanced by applying on the intumescentmixture layer an additional coat of aqueous melamin resin, to whichaccelerator (2-3%) has been added as described in Example 2-1 and 2-2.

SUMMARY OF MATERIALS AND AGENTS USED IN EMBODIMENTS % Range by totalComponent weight An intumescent mixture including: A colloid formingsolution 25-60% wherein the solvent is water containing 3-5% of acolloid forming water soluble polymer, preferably derivatized cellulose,a carbohydrate, or a protein. Intumescent base materials, 15-40%including a foaming agent, a blowing (also oxygen spread limitingreagent) agent and a charring agent; such foaming agent is selected fromthe group consisting of monoammonium phosphate, diammonium phosphate,and ammonium polyphosphate; such charring agent is selected from thegroup consisting of glycerol, sorbitol, starch, pentaerythritol,dipentaerythritol, dextrin, and polysaccharides; such blowing agent isselected from the group consisting of melamine, urea, dicyandiamide,guanidine, glycine and short chain aminoacids. Flame spread reductionagents; such as 1.5-5.0% aluminum hydroxyde [Al (OH)3], ammoniumorthophosphate, zinc oxide (ZnO), or antimony oxide (Sb2O3). Thermalresistance enhancer agents, such 1.5-7.0% as kaolin, ground glass.Thermal transmission reduction and refractory  3-15% agents, such aszirconium dioxide (ZrO2), titanium dioxide (TiO2), silicon dioxide(SiO2), aluminum trioxide (Al2O3), zinc oxide, milled fibers. Elasticityagents and fillers (glass fibers,  0-10% vermiculite, perlite, or thelike) Polarity modifying agents: water-based resins  0-50%(melamine-formaldehyde resins, selected from the group consisting ofaqueous partially alkylated hexamethoxymethylol melamine, or partiallyalkylated hexamethoxymethylol melamine containing traces of formaldehyde(“AEROTEX 3430” and “AEROTEX M3” from BF Goodrich or equivalent) Resinpolymerization activator (diammonium 0-5% phosphate, ordiammoniumphosphate with hexamethylene diamine) Primer for colloidapplication (silicone based)-coating

APPLICATIONS OF THE PRESENT INVENTION

The fire retardant coating material of the present invention can be usedfor applications on diverse kinds of solid substrates, both natural,synthetic, and metallic. The product is comprised of an intumescent baseand a primer resin. The intumescent base can be used for naturalsubstrates and some synthetic substrates, whereas the intumescentbase-primer resin mixture is used on substrates that have low chemicalaffinity to the intumescent base. The product has no human toxicity.

Natural substrates are cellulose, paper by-products, wood, woodby-products, sheetrock, rubber, metals, etc. Such substrates are thebase of building structures and materials, structural building elements,furniture, home furnishings, rubber hoses, ceiling tiles, columns andbeams, wood frames, walls, etc.

Synthetic substrates are vinyl, PVC, polystyrene, styrofoam, syntheticrubber, polyvinyl, epoxy, synthetic resins, etc. Such materials are usedin the production of hoses, pipes, PVC wrappings, toys, household items,building materials, laboratory and professional items, etc.

The present product can thus be used for fire and flame spreadprotection in buildings and their supporting structures, bothresidential, industrial, and public, in building materials, to protectthe interior and exterior of walls, supporting structures, metalsurfaces, garages, ceilings, hung ceilings, window frames, woodpaneling, carpet backing, roofing, attics, electrical wires, furniture,safes, file cabinets, toys and the like. In the transportation industryit can be used to protect both the carriers and transported objects, toprotect chemicals and other items transported in styrofoam. In industryit can be used to make tubes and pipes fire retardant, difficult to meltunder sustained heat.

In households the product is applied like a paint by brushing or roller,or by spraying. In industrial applications high volume applications arerecommended. In the construction industry pretreatment is possible.

1. An aqueous colloidal fire and flame retardant intumescent mixturecomprising: a) a water-based colloidal solvent comprising a colloidforming water soluble polymer, comprising a carbohydrate or a protein;and, b) said colloidal solvent further comprising a foaming agent, ablowing agent, and a charring agent to form an intumescent base; and, c)said intumescent base further comprising a flame spread reductionmaterial, a thermal transmission reduction and refractory material, athermal resistance enhancer, and an elasticity agent to form anintumescent mixture.
 2. The intumescent mixture of claim 1 comprising:a) 3-7.5 wt % of said colloid forming carbohydrate or protein; b) 10-30wt % of said foaming agent; 20-25 wt % of said blowing agent; 25 wt % ofsaid charring agent; c) 5.0-7.5 wt % of said flame spread reductionmaterial; 18-27 wt % of the thermal transmission reduction andrefractory material; 1.5-7.7 wt % of the thermal resistance enhancer;and 10 wt % of the elasticity agent.
 3. The intumescent mixture of claim2, wherein: a) said carbohydrate comprises derivatized cellulose; and,b) said foaming agent comprises monoammonium phosphate and diammoniumphosphate, or ammonium polyphosphate; said charring agent comprisesglycerine, starch, dextrin, sorbitol, pentaerythritol, ordipentaerythritol; said blowing agent comprises melamine, urea,dicyandiamide, glycine, guanidine, or aminoacids; and, c) said flamespread reduction material comprises aluminum hydroxide, ammoniumorthophosphate or antimony oxide; said thermal transmission reductionand refractory material comprises zirconium dioxide, aluminum trioxide,silicon dioxide, titanium dioxide or milled fibers; said thermalresistance enhancer comprises kaolin and ground glass; said elasticityagent comprises vermiculite or perlite.
 4. The intumescent mixture ofclaim 3, further comprising a polarity modifying agent to modify thepolarity of the mixture.
 5. The intumescent mixture of claim 4, saidpolarity modifying agent comprises 20-50 vol % melamine formaldehyderesin, to form by polymerization a loose adhesive molecular network. 6.The intumescent mixture of claim 5, further comprising an accelerator toaccelerate polymerization.
 7. The intumescent mixture of claim 6,comprising 3-5 wt % accelerator in said resin and 1 part by volume ofsaid accelerated resin in 2-5 parts by volume of the intumescentmixture.
 8. The intumescent mixture of claim 7, wherein saidmelamine-formaldehyde resin comprises partially alkylated hexamethylolmelamine or partially alkylated trimethylol melamine; and theaccelerator comprises diammonium phosphate or hexamethylene tetramine.